FM transmitter converts MP3 music from your music device into FM signal with a 3.5mm audio plug in a blank FM station, so that your car FM radio can receive the FM signal in the same station and output music through your car audio systems. Besides, it has a 5V 2.1A output USB charging port which can charge your phone or MP3 at the same time. With this FM transmitter, you will be able to share MP3 music from your portable audio device on long car trip. Just like to build an individual music station, it is very interesting and popular among the young.